In recent years, the power module has been in growing demand for smaller size and better heat release in order to achieve improved space efficiency. Also, there has been demand for lower energy cost and reduced environmental load of the power module. Developed to meet these demands are intelligent power modules (IPMs), which are circuit devices having both a control unit and a power device mounted on a single metal substrate.
FIG. 11 is a cross-sectional view schematically illustrating a structure of a conventional circuit device. An insulating resin layer 510 is formed on a metal substrate 500 made of aluminum or the like. Wirings 520 made of copper, for instance, are formed on the insulating resin layer 510. Further, circuit elements 530, such as transistors and ICs, and passive elements 540, such as resistors and capacitors, are mounted on the wirings 520 through the medium of solder 551, thereby realizing a predetermined circuit. When the circuit elements 530 are to be mounted face-up, the electrodes of the circuit elements 530 are connected to the wirings 520 by wire bonding using gold wire 532. An external lead 550 is connected to an external electrode terminal 552 through the medium of solder 551, and a part of the external lead 550 is exposed outside from a sealing resin member 580 to be described later.
Note that the insulating resin layer 510 is provided with an opening which allows a part of the metal substrate 500 to be exposed. The exposed part of the metal substrate 500 is connected to a wiring 520a which is connected to ground potential. As a result, the metal substrate 500 functions as a shield even when the circuit elements 530 are in operation, so that malfunction of the circuit and occurrence of noise are being suppressed.
An overcoat 560 is formed to cover solder joints, gold wires 532, circuit elements 530, and passive elements 540.
The sealing resin member 580 includes a support 582 and a sealing resin layer 584. The support 582 and the sealing resin layer 584 are both made of a thermoplastic resin. The sealing resin 580 is formed by injection molding in which the metal substrate 500 placed on the support 582 is coated with the sealing resin layer 584. This produces a circuit device of a full-molded structure.
[Patent Document 1] Japanese Patent Application Publication No. 2005-277174.